• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.2
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• pp.44-49
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• 2011

A study of the fatigue life of copper alloy which was used in inner jacket of regenerative cooling chamber of liquid rocket engine has been performed. Generally used life prediction methods -original universal slopes method, modified universal slopes method, Mitchell's method, B$\"{a}$umel and Seeger's method, and Ong's method- have been used for predicting the fatigue data. It was found that the novel life prediction method which was modified from Ong's method was suggested since almost all data have not been predicted well with the widely used methods. The suggested modified Ong's method predicted well within 3X scatterbands.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.89-92
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• 2010

A study about the fatigue life of copper alloy which is used in inner jacket of regenerative cooling chamber of liquid rocket engine has been performed. Generally used life prediction methods-original universal slopes method, modified universal slopes method, Mitchell's method, Baumel and Seeger's method, and Ong's method-have been used for predicting the fatigue data. It was found that the novel life prediction method which is modified from Ong's method was suggested since almost all data have not been predicted well with the widely used methods. The suggested modified Ong's method predicted well within 3X scatterbands.

• Korean Journal of Metals and Materials
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• v.48 no.10
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• pp.942-950
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• 2010

The microstructure and mechanical properties of a Cu-Fe-P copper alloy processed by differential speed rolling (DSR) were investigated in detail. The copper alloy, with a thickness of 3 mm, was rolled to 50% reduction at ambient temperature without lubrication with a differential speed ratio of 2.0:1 and then annealed for 0.5h at various temperatures ranging from 100 to $800^{\circ}C$. Conventional rolling was performed under the same rolling conditions for comparison. The shear strain introduced by the conventional rolling process showed positive values at the positions of the upper roll side and negative values at the positions of the lower roll side. However, the result was zero or positive values at all positions for samples rolled by DSR. The effects of DSR on the microstructure and mechanical properties of the as-rolled and subsequently annealed samples are discussed.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.69-76
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• 1999

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of upset pressure on friction weldability. Under the condition of friction time 0.8sec, upset pressure 150MPa, the tensile strength and Charpy impact value of the friction welded joint were 336MPa, $400KJ/m^2$ respectively. And highest temperature of the weld measured was below $800^{circ}K$ which is very lower than melting point of Cu($1356^{circ}K$). Under the same conditions, W grains picked up in Cu matrix from Cu-W profitably affected on these mechanical fracture, and were dispersed in Cu by plastic flow during brake time.

• Journal of the Korean institute of surface engineering
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• v.32 no.6
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• pp.695-702
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• 1999

We have explored the factors affecting the resistivity of Cu (Mg) alloy, which was prepared by sputtering. The results show that the resistivity is a function of Mg content, annealing temperature, annealing time, and Cu-alloy thickness. Addition of Mg to copper increases the resistivity through solute scattering. In addition, increasing Mg content promotes the interfacial reaction between Mg and SiO$_2$ to produce the free silicon and the generated free silicon dissolves into copper, resulting in a significant increase of resistivity. Furthermore, increasing oxidation temperature rapidly decreases the resistivity at the initial stage of oxidation and then continues to increase the resistivity to the saturation value with increasing oxidation time. The saturation value depends on the residual Mg content and the thickness of the alloy. TEM and AES analyses reveal that dense, uniform MgO grows to the limiting thickness of about $150\AA$. However, interfacial MgO does not show the limiting thickness, instead continues to grow until Mg is completely exhausted. From these facts, we proposed the maximum available Mg content needed to from the dense MgO on the surface and suppress the excessive interfacial reaction.

• Korean Journal of Materials Research
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• v.28 no.2
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• pp.113-117
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• 2018

Effects of annealing temperature on the microstructure and mechanical properties through thickness of a cold-rolled Cu-3.0Ni-0.7Si alloy were investigated in detail. The copper alloy with thickness of 3 mm was rolled to 50 % reduction at ambient temperature without lubricant and subsequently annealed for 0.5h at $200{\sim}900^{\circ}C$. The microstructure of the copper alloy after annealing was different in thickness direction depending on an amount of the shear and compressive strain introduced by rolling; the recrystallization occurred first in surface regions shear-deformed largely. The hardness distribution of the specimens annealed at $500{\sim}700^{\circ}C$ was not uniform in thickness direction due to partial recrystallization. This ununiformity of hardness corresponded well with an amount of shear strain in thickness direction. The average hardness and ultimate tensile strength showed the maximum values of 250Hv and 450MPa in specimen annealed at $400^{\circ}C$, respectively. It is considered that the complex mode of strain introduced by rolling effected directly on the microstructure and the mechanical properties of the annealed specimens.

• Journal of Korea Foundry Society
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• v.3 no.4
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• pp.256-261
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• 1983

In this study, the variations of tensile strength and yield strength of Al-20% Si alloy were studied. Copper, magnesium and nickel as alloying elements added from 1% to 3% respectively. The temperature range was from room temperature to $350^{\circ}C$. The refinement of primary silicon crystal was treated with phosphorous addition. The results obtained are as follows: 1. Tensile strnegth and yield strength showed more increased strength in refining treated alloy than that of in nonrefining alloy at elevated temperature. 2. Tensile strength and yield strength were increased with the contents of copper. Tensile strength showed the maximum at $150^{\circ}C$, but yield strength was decreased with increasing temperature. 3. The effect of magnesium addition on tensile strength and yield strength showed the maximum at 1% addition and $150^{\circ}C$. 4. Tensile strength and yield strength showed a slight increase with the content changes of nickel and they were decreased with increasing temperature.

• Journal of Powder Materials
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• v.10 no.3
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• pp.164-167
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• 2003

The mechanical alloying effect has been studied on the three Cu-based alloy systems with a positive heat of mixing. The extended bcc solid solution has been formed in the Cu-V system and an amorphous phase in the Cu-Ta system. However, it is round that a mixture of nanocrystalline Cu and Mo Is formed in the Cu-Mo system. The neutron diffraction has been employed at a main tool to characterize the detailed amorphization process. The formation of an amorphous phase in Cu-Ta system can be understood by assuming that the smaller Cu atoms preferentially enter into the bcc Ta lattice during ball milling.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.444-446
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• 1999

The structure and composition of anodic films, formed on 6063 commercial aluminium alloy at constant current density of $1.5A/^dm2$ with various superimposed cathodic current ratio, in the range 0~33%, in the 11% $H_2SO_4$ with various concentration of $CuSO_4{\cdot}5H_2O$, in the range 0~75 g/l, without cathodic current are generally porous-type and no sign of Cu co-deposition appearance, suggesting that cathodic current is an important factor in the Cu co-deposition. Comparison with the anodic film thickness measurement results obtained from anodic film formed by direct anodic current and anodic film formed by superimposed various portion of cathodic current, the portion of cathodic current of input current increases with decrease of anodic film thickness and increases with increase of concentration of $Cu_2S{\;}and{\;}Cu_2O$ in the anodic film.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.414-417
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• 2003

A copper-clad aluminium composite bar is lighter and less expressive than a commercial copper alloy bar. Copper-clad aluminium composite bar can be fabricated by hot hydrostatic extrusion process. In this work, the effect of die angle on the compressive properties of copper-clad aluminium composites fabricated using hydrostatic extrusion process was investigated experimentally. The results showed that optimum half die angle was in the range of 40$^{\circ}$ to 50$^{\circ}$ for an extrusion ratio of 19. The results also showed that the half die angle had little influence on the compressive strength of copper-clad aluminium composites. A diffusion layer increased with increasing die angle.